Oil Suddenly Leaking From Multiple Seals And Shifter

That is actually a very common problem with Yanmar tractors and it almost always caused by a bug building a nest in your breather tube. The breather tube is the small curved hook looking pipe right behind the seat. You can unscrew the tube and clean it out with a small wire.

As the transmission warms during normal operation or even just from sunshine warming them in the afternoon, the gasses inside the housing start to expand. If the transmission area can not vent out the expanding gasses then it builds up pressure and forces the oil out of the seals and, especially, the shifter boots.